: I just bought a home with a jacuzi tub in the bathroom. It is immaculate, however when I run the jets, black gunky stuff comes out the jets.It looks like mold or mildew. I have run it several times in one day and the stuff coming out decreases after the third fill and drain. However I don't use every day and the next time I run it the same thing hapens. How can I prevent this from happening? I have tried using dishwashing detergent as a cleaner. Any other suggestions?